HOUSTON – Firefighters scrambled to save nearby homes as flames devoured a warehouse in west Houston.

Now, arson investigators are investigating what sparked the inferno.

“At first it was a small fire,” said Lidonny Gonzalez. “It spread like that.”

MORE: Massive 4-alarm blaze erupts in W. Houston

Gonzalez heard a popping noise and went outside to see flames in his neighbor’s backyard.

“There was barrels that started flying out of there, like oil barrels,” Gonzalez said.

Photos: 4-alarm warehouse fire in Spring Branch

Arson investigators are examining a charred shed in a backyard where they believe the fire started. The flames melted part of the siding of the home. Fire officials said it appears the backyard was home to an auto body shop.

“That’s where we are going to start investigating this fire,” said District Fire Chief Robert Branch.

No one was injured in the massive blaze.

“Thank God everyone is OK,” said Elizabeth Rendon.